1. Field of the Invention. The present invention relates to a fuel additive analyzer system and process, and more particularly to an improved apparatus for, and method of, determining the presence of oxygen enhancing additives in a fuel supply and the oxygen content of such fuel supply by weight.
2. Summary of Related Art. The enactment of the Federal Clean Air Act Amendments of 1990 requires the each state to sell oxygenated gasoline in areas where the air quality does not meet the federally mandated National Ambient Air Quality Standards (the "Standards"). This requires certain metropolitan areas with high levels of carbon monoxide and other air pollutants to sell, during the portion of a year in which the area is prone to high concentration of air pollutants, fuels containing such levels of oxygen as necessary to provide for attainment of the Standards. The addition of oxygen to the fuel supply results in a cleaner burning fuel with less air contamination.
The Standards are effective in 1993 and the state and federal governments are working to identify the metropolitan areas that do not meet the Standards. As additional metropolitan areas fail to meet the Standards, the requirements for supplying oxygenated fuel will increase throughout the United States.
A number of additives have been approved for supplying the additional oxygen to the fuel supply. However, the primary additives in use are (1) Ethyl Alcohol and (2) Methyl Tertiary Butyl Ether ("MTBE"). The amount of oxygen to be added to the gasoline varies depending on the level of contaminants in the fuel and other steps being taken to improve the quality of the air. However, in the metropolitan areas not in compliance with the Standards, the statutory and regulatory provisions require the fuel supply must have the specified oxygen levels in order to permit the sale of the fuel.
At this time, there is a need for a convenient, accurate, and reliable means for testing and documenting the oxygen additives in gasoline and other fuels. A portable analyzer would be used not only by government inspectors for compliance purposes, but also by service stations, oil companies, and independent consultants to test and independently document compliance with the Standards.
Oxygen content in oxygenated gasoline has historically been measured by gas chromatography or infra-red spectrophotometry. Both of these methods are quite complex and require calibration based on a blended reference sample using the additive type which is in the fuel being tested. In addition, these methods are also more conducive for laboratory and production oriented testing, and not for portable use in testing oxygen levels at service stations and other field locations.
The present invention utilizes dielectric properties of the additives, and resonant frequency and DC conductivity measurements to determine the composition of the fuel being tested. The fuel dielectric constant is a function of the oxygen level in the fuel and the additives used to achieve such oxygen level. A microprocessor programmed with a special algorithm may be used to identify the additives in the fuel and the percentage weight of such additives.
A number of monitoring systems have been developed for use in automobiles, and in other applications, for monitoring air-fuel ratios and fuel compositions. U.S. Pat. No. 4,389,881 to Butler et al discloses a method for determining an air to fuel ratio for an internal combustion engine by measuring the electromotive force of an oxygen sensor, the total pressure of a sample gas stream, and the known oxygen addition rate.
U.S. Pat. No. 4,578,172 shows a detector for use in measuring the concentration of oxygen in exhaust gas from a burning device, such as an internal combustion engine or gas burner. An oxygen sensor is used to detect the change in electromotive force that is produced by the difference between the partial oxygen pressure of the exhaust gas and that of atmospheric air.
The air fuel ratio detector disclosed in U.S. Pat. No. 4,629,535 to Oyama et al. includes an oxygen ion conductive solid electrolyte, first and second electrodes on each side of the electrolyte, a diffusion resistor exposed to the measured gas, and means for supplying a current between the first and second electrode. The withdrawal current value is used to determine the air-fuel ratio.
U.S. Pat. No. 5,103,184 to Kapsokavathis et al teaches a fuel composition sensor apparatus for signaling an engine control computer in an automobile operating on an unknown, variable concentration of two fuels, such as gasoline and alcohol.
U.S. Pat. No. 5,103,181 to Gaisford et al discloses a system and process for determining the compositional makeup of multicomponent fluids, solids, and mixtures thereof whose components have different electrical impedance properties. The system is suitable for use in a variety of industrial processes where the fluids and solids may be stationary, moving in batches, or flowing continuously. Radio frequency bridge techniques are used to parameterize the complex dielectric properties of the components in an electrically isolated, physically open structure.